The invention relates to a method for controlling a power supply system of an automotive vehicle, comprising at least one battery and a battery managing unit adapted to monitor the state of charge of said battery. The invention also relates to a power supply system adapted to such a method.
Automotive vehicles are generally equipped with one or several batteries. When the vehicle is left unused for a period of time, batteries may become depleted for various reasons. First of all, even when a vehicle is in an off-state, there usually are a number of electric or electronic devices which are connected to the batteries and which draw small currents from the battery. For example, if the vehicle is equipped with a remote keyless door locking system, the electronic control unit for that system needs to stay active to control the system so that it can detect that an authorized user wants to access to the vehicle. Also, a battery may be subject to self-discharge when the vehicle is not used fir a relatively long period. In both cases, this might result in the vehicle not being operational when the user wants to use it. Moreover, if such a period lasts too long, resulting in a strong depletion of the battery, such battery discharging can damage the battery and can lead to a deterioration of its charging and discharging abilities. In case a company owns several vehicles, deterioration of batteries can lead to the inability to move some vehicles and the need to replace several batteries, inducing relatively high maintenance costs and financial losses.
This issue is particularly important in the domain of hybrid automotive vehicles, which comprise a high voltage battery, which delivers the electric power needed for traction purposes, and a low voltage battery, which usually delivers power to on-board electronic systems and to low power on-board electric auxiliaries, such as vehicle lights, windshield wipers, etc. . . . . To limit the risk of damaging the high voltage battery, it is known, for example from JP-2007.161,000, to detect a low state of charge of the low voltage battery and to recharge the low voltage battery by transferring electric power from the high voltage battery, thanks to a direct current/direct current (DC/DC) converter.
Such system does not prevent damaging of a battery, it can only postpone it for some time, hoping that during that extra time somebody will use the vehicle or at least maintain it. Such system does not allow for example to perform maintenance operations in due time before the low voltage battery reaches a too low state of charge level to operate properly.
It is desirable to provide a new method for controlling a power supply system of an automotive vehicle which allows to inform a remote system or person that a battery of the vehicle is likely to be damaged, so as for example to allow the system or person to perform maintenance operations or to take other actions before the damage is too important.
An aspect of the invention concerns a method for controlling a power supply system of an automotive vehicle, comprising at least one battery and an associated battery managing, unit adapted to monitor the state of charge of said battery. This method is characterized in that it comprises the following steps:
a) during an off state of the vehicle, monitoring of the state of charge level of the or each battery by its associated battery managing unit.
b) if the state of charge monitored at step a) reaches a low state of charge threshold, activation of an on-board communication device adapted to emit a critical state of charge level alarm to be received by an off-board reception device.
Thanks to an aspect of the invention, if a battery on the vehicle is approaching a critical state of charge level, meaning that damage could appear on the battery, a communication device of the power supply system is activated so as to send out an alarm signal. Through this alarm, it is possible to warn a system or a person, for example the owner of the vehicle, that a battery of his vehicle may be damaged if the vehicle is left in its off state any longer and if nothing is done to recharge the battery.
According to further aspects of the invention which are advantageous but not compulsory, such a method may incorporate one or several of the following, features.                At step a), the respective states of charge of a high voltage battery and a low voltage battery of the vehicle are monitored, and whereas the method comprises a further step of:        
c) activation of a converter electrically connecting the high voltage battery to the service battery.                The method comprises a further step of:        
d) If, at step a), it is determined that the state of charge of any of the high voltage battery and the low voltage battery has reached a low threshold, then recharging of said battery by the other battery through the DC/DC converter.                Step d) is conditional upon a recharging instruction, for example for allowing or inhibiting such recharging, received by the on-board communication device from an off-board communication device        The on-board communication device implements a remote wireless communication protocol.        
The invention also concerns, according to an aspect thereof a power supply system for an automotive vehicle, comprising at least one battery equipped and an associated battery managing unit adapted to monitor the state of charge of said battery. This power supply system is characterized in that the battery managing unit associated to the or each battery is adapted to monitor the state of charge of said battery when the vehicle is in an off state, and in that it comprises means to emit a critical state of charge alarm to be received by an off-board reception device, when the state of charge monitored by the battery managing unit associated to the or each battery reaches a low threshold.
According to further aspects of the invention which are advantageous but not compulsory, such a power supply system may incorporate one or several of the following features:                The power supply system comprises a high voltage battery and a low voltage battery, and wherein it comprises means to charge the high voltage battery with the low voltage battery when the state of charge of the high voltage battery reaches a low threshold, or to charge the low voltage battery with the high voltage battery when the state of charge of the low voltage battery reaches a low threshold.        The means to charge the high voltage battery or the low voltage battery comprise a DC/DC converter.        The DC/DC converter comprises a dedicated control unit adapted to communicate with the respective battery managing unit(s) associated to the high voltage, battery and the low voltage battery.        The means to emit a critical state of charge alarm comprise a communication device adapted to send alarms to a server off-board the vehicle.        The communication device is adapted to receive instructions from the server.        The communication device is wireless, for example using, a GPRS communication protocol.        